A first prior art apparatus and method for removing a calculus includes a bathtub wherein a patient is seated in a pool of water and includes two transducers which are positioned to focus on the calculus and to emit compression waves on opposite sides of the patient. These waves are focused on the calculus, and the absorption of these waves by the calculus tends to fatigue the calculus. Microscopic cracks form both within and outside the calculus after each blast caused by a lithotriptor that connects to the transducers. As each blast damages the calculus, it is finally fragmented into various sized particles. In some cases, more than 1000 blasts are needed before the calculus can be completely broken down and flushed from the patient which can take a few hours. One problem with the first prior art method is that it can leave the patient with external bruises or in some cases, can cause the kidneys or other organs to bleed.
A second prior art method of calculus removal involves drinking by the patient of dissolving agents. One problem with this method is that it can only be successful if the stones are of a certain biological make-up.
A third prior art device and method can be used if the calculus is small enough to be removed with a catheter that has a fixed basket on the end thereof. This catheters basket has a plurality of wires, usually a group of four wires, which are configured in such a way as to form a basket that will grip the calculus at four possible points or surfaces. The wires which form the basket structure are relatively tiny wires that are twisted together, thereby creating a small flexible bundle of wires. The flexibility of the wire bundles helps grip a calculus with an irregular surface contour. One problem with this method is that it is not effective when attempting to remove relatively large stones.
A fourth prior art device can remove relatively large stones, which are too large to be removed by a basket. This fourth device has a catheter which has an alligator-shaped clip device that is located at the end thereof. This clip Call be manipulated to hold a calculus in its jaws. The calculus, which is too large to be removed, can be crushed into smaller fragments by a connecting control mechanism, which forces the alligator-shaped clip to clamp down and crush the calculus. These fragments,. if small enough, can then be flushed from the body, and the larger remaining fragments can be removed with a basket, or crushed a second time with the alligator-shaped clip. One problem with this fourth prior art device is that stones may be highly calcified, and in attempting to crush the calculus the alligator-shaped clip may bend and fracture, or cause the wires connected to the alligator-shaped clip to be stressed beyond their elastic limit and finally fracture. If this should occur, the specialist or practitioner has to surgically remove not only the fragments of the alligator-shaped clip or wires, but the undamaged calculus. Often, a patients health will indicate that performing such surgery is too risky.
A fifth prior art device has a catheter which has a sonic or ultrasonic wire that extends through the catheter. This fifth device can disintegrate various types of stones. Fracturing of these stones is accomplished because of the ability of the end of the sonic wire to hammer the calculus, like that of a jack hammer, or to erode the calculus by cavitation forces which are formed at the tip of the sonic wire. One problem with this fifth device is that it is not chosen for a lithotripsy procedure, because of the inherent nature of these wires to fracture due to heat-induced metal fatigue or because of the possibility that the wire will slip from its normal position and pass into an organ or vessel thereby complicating the whole procedure.